/Engine/Plugins/MeshPainting/Source/MeshPaintingToolset/Public/MeshPaintHelpers.h
Retrieves the number of bytes used to store the per-instance LOD vertex color data from the mesh component
void GetInstanceColorDataInfo ( const [UStaticMeshComponent](API\Runtime\Engine\Components\UStaticMeshComponent) * StaticMeshComponent, int32 LODIndex, int32 & OutTotalInstanceVertexColorBytes )